There are a variety of applications in which a component operates in a high temperature environment. For example, during the operation of a turbine engine, many components are exposed to high temperature gases. These hot gas path components must be able to withstand such high temperatures. To that end, the components can be made of materials that are well suited for high temperature applications. One suitable class of materials is refractory ceramics. Various turbine components, such as heat shields, have been made of refractory ceramics. While they have proved to be durable in a gas turbine environment, refractory ceramics have limited strength and strain tolerance, which are barriers to their application to more structural components like turbine vanes.
Another suitable group of materials is ceramic matrix composites (CMC). CMCs offer higher strengths, but they are expensive and are difficult to fabricate into complex shapes. One CMC fabrication method involves laminating fabrics with the fibers oriented essentially parallel to the major surface planes of the component, essentially forming a skin structure. Another CMC fabrication method involves stacking a plurality of CMC laminates to form the desired shape (i.e., with the CMC defining the entire surface, but with fibers oriented in planes normal to the component surface). There are several constraints and drawbacks associated with these constructions. Without internal cooling, many CMC components cannot endure the extreme operational temperatures. When internal cooling is provided, the components cannot endure the thermal gradients that can develop across the components during engine operation. As a result, the CMC components require an insulating coating to reduce these thermal gradients. For example, turbine airfoils made of oxide CMCs are usually protected by a thick thermal barrier coating.
As will be appreciated, both refractory ceramics and CMCs can provide significant benefits in the context of turbine engines or in other high temperature applications. However, neither material system by itself is ideal. Thus, there is a need for a construction system and method that can incorporate both refractory ceramics and CMCs so that the advantages of both material systems can be realized while the limitations of each system are minimized.